Multimodal image characterization of paravenous atrophy

Objective: The objective is to describe a clinical case of paravenous atrophy using a multimodal image. Methods: A 48-year-old man was visited and followed in the ophthalmology department of Hospital Clinic (Barcelona). Visual acuity, slit-lamp exam, retinography, autofluorescence, visual field, optical coherence tomography, and electrophysiology test were performed. Results: The patient had a history of Behcet’s disease. Autofluorescence revealed hypoautofluorescence at the paravenous region, th visual field was also altered and electrophysiologic test were reduced. Conclusion: Paravenous atrophy is a rare entity not well described currently. Patients are frequently misdiagnosed. Multimodal image could help to characterize this condition properly and improve the management.


Introduction
Pigmented paravenous retinochoroidal atrophy (PPRCA), described as retino-choroiditis radiata in 1937 [1], is an uncommon disease with unknown etiology characterized by bilateral retinal pigment epithelium (RPE) and choroidal atrophy along retinal veins, generally without macular involvement. The main physiopathologic theory supports that choroidal thinning precedes development of the RPE atrophy [2]. PPRCA is commonly bilateral and symmetric, but appears to have variable expressivity and a spectrum of mild to severe ophthalmoscopic change [3]. Diagnosis is often fortuitously made during a routine exam and is based on a typical and characteristic fundus appearance. The principal differential diagnosis has to be done with typical retinitis pigmentosa (RP) [4]. Non-invasive imaging techniques including retinography, fundus autofluorescence (FAF), swept source optical coherence tomography (SS-OCT), and OCT angiography (Angio-OCT) are now available to the study of retinal dystrophies like this. We present a clinical case of PPRCA in association with Behcet's disease through multimodal study.

Case description
A 48-year-old man of Caucasian origin and ex-smoker came to our ophthalmology department with visual and campimetric worsening in both eyes (OU) since the last two months. He had a history of Behcet's disease with severe ocular involvement (retinochoroidal) and bipolar aphtosis, previously treated with immunosuppressants and biologic therapy: adalimumab (ADA), infliximab, and azatriopine (AZA). At that time he was stable (no signs of activity) and following treatment with ADA 40 mg/month. His best corrected visual acuity (BCVA) was 20/32 (Snellen chart) in his right eye (OD) and 20/63 in his left one (OS). Anterior segment was unremarkable for both eyes (OU). Fundus evaluation showed pigment clumps along the retinal veins with variable chorioretinal atrophy extending from the disc up to the equator in both eyes (clinically more evident in OS). Fundus autofluorescence (FAF) imaging revealed hypo-autofluorescent areas corresponding to the atrophic patches over the posterior pole ( Figure 1 and Figure 2). SS-OCT showed a preserved foveal profile and great macular atrophy in OU, but serious involvement of the retinal outer layers in the left eye ( Figure 3 and Figure 4). In Angio-OCT, severe involvement of the ellipsoid, choriocapillar, and avascular layers could be appreciated in OS.  Electroretinography (ERG) showed diffuse response peaks in OU, with marked peripheral involvement, in addition to an increase in latency and a decreased amplitude in scotopic and photopic stimulation resulting from a generalized and advanced bilateral photoreceptor dysfunction accompanied by macular anomalies. In visual field (VF) 24.2, there was a higher altitude defect in OR and a temporary defect in OS. A clinical diagnosis of pseudoparavenous atrophy secondary to Behcet's disease OU was done.

Discussion
PPRCA is a rare entity that is currently not well described.
The cause of this condition may be unknown or idiopathic, although a dysgenetic, degenerative, hereditary etiology or even an inflammatory cause hav been hypothesized [5]. PPRCA primarily involves the RPE, with secondary atrophy of the underlying choroidal vasculature [6], [7], [8].  [9]. In the case that we present, paravenous hypoautofluorescence could be appreciated. SS-OCT scans normally reveal thinning of retinal layers with increased backscattering and disorganization of the RPE choriocapillaris complex. In many occasions, as we can see in our case, retinal and choroid slimming is such severe that scleral looks like very thick. Hyperreflective plaques with underlying shadowing corresponded to the pigment clumps observed clinically [10]. OCT-A study is not correctly defined yet and we do not find explanatory signs in our patient. Visual field shows peripheral scotomas corresponding to areas of chorioretinal atrophy. In advanced cases, the macula is also involved, so central visual field strategies as 10:2 VF should be used. Electrodiagnostic data are variable and nonspecific, ranging between normal and mildly affected, even markedly subnormal or a totally extinguished electroretinogram (ERG) [11]. This variation may signify that several conditions can present in this manner. In the case that we present, we can observe an alteration in photopic and scotopic response, more marked at periphery but with macular involvement too. We have to keep in mind that this entity could present as an isolated phenomena or be associated to other ocular disorder as Behcet's disease (as we found in our case), tuberculosis or syphilis [12].

Conclusion
In summary, PPRCA is an uncommon disease, so exhaustive image studies must be performed for its correct definition and management. More cases would be needed to clarify the etiology of this entity and precise progression.